Pump

ABSTRACT

A circulating pump with an impeller disposed in a pump housing, by which a fluid can be delivered from a pump inlet of the pump housing to a pump outlet of the pump housing. The circulating pump includes an electric motor, the rotor of which is mechanically coupled to the impeller via a shaft such that that the impeller can be placed into an appropriate rotating movement by rotation of the rotor, and cools the rotor of the electric motor by a thermosiphon in the shaft, wherein the impeller serves as a heat sink for a working medium of the thermosiphon.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage of International ApplicationNo. PCT/EP2009/059235, filed Jul. 17, 2009 and claims the benefitthereof. The International Application claims the benefits of GermanApplication No. 102008046293.4 filed on Sep. 8, 2008; both applicationsare incorporated by reference herein in their entirety.

BACKGROUND

Described below is a pump, in particular a circulating pump, which hasan impeller in a pump housing and with which a fluid can be deliveredfrom a pump inlet of the pump housing to a pump outlet of the pumphousing. A rotor of an electric motor is mechanically coupled to theimpeller via a shaft such that, by rotation of the rotor, the impellercan be placed into a corresponding rotating movement. Furthermore, thepump cools the rotor of the electric motor.

In order to increase the efficiency of circulating pumps, it is known toproduce the circulating pumps from particularly high-quality materialsin order to improve the efficiency thereof. Circulating pumps of thistype are referred to as high efficiency circulating pumps. Thus, forexample, short-circuit bars of the rotor are manufactured from copperinstead of the aluminum which is frequently used. However, these highefficiency circulating pumps have the disadvantage of high costs.

SUMMARY

An aspect is to provide a pump in which the efficiency can be increasedin a simpler and more cost-effective manner.

A pump includes an impeller in a pump housing and with which a fluid canbe delivered from a pump inlet of the pump housing to a pump outlet ofthe pump housing. The pump furthermore includes an electric motor, therotor of which is mechanically coupled to the impeller via a shaft suchthat, by rotation of the rotor, the impeller can be placed into acorresponding rotating movement. Furthermore, cooling of the rotor ofthe electric motor is provided by a thermosiphon which is arranged inthe shaft, the impeller serving as a heat sink for a working medium ofthe thermosiphon.

The pump makes use of the fact that better cooling of the rotor inelectric motors results in an increase in the efficiency. This effect ismade use of in the pump and a shaft thermosiphon is inserted in therotor shaft. Cooling of the shaft also results in cooling of the rotorof the electric motor, thus resulting in the desired increase inefficiency. The heat conducted away from the rotor is dispensed via thethermosiphon to the pump wheel which is located in a fluid, for exampleheating water, the pump wheel being used and designed as a condenser.This has the consequence that heat lost from the rotor of the electricmotor is recycled into the fluid circuit. If the latter is, asmentioned, a heating circuit, then the efficiency thereof can also beincreased, since heat is supplied to the heating water.

The pump furthermore has the advantage of being able to be produced morecost-effectively by comparison to the high efficiency circulating pumpsknown from the related art, since use can be made of known materials,such as short circuit bars of the rotor made from aluminum. Furthermore,however, the efficiency of already optimized high efficiency circulatingpumps can also be further increased. Although a smaller increase inefficiency than with conventional circulating pumps should beanticipated owing to the losses from high efficiency circulating pumpsalready being lower, nevertheless the provision of a thermosiphon in theshaft and the use of the impeller as a heat sink permit a furtherimprovement in the efficiency.

According to an advantageous refinement, in order to form thethermosiphon in the shaft, a recess is provided, the recess extending inthe longitudinal direction and in which the working medium circulatesowing to a change in the state of aggregation between liquid andgaseous. It is expedient in this case if the recess extends over theentire width of the rotor of the electric motor so that as good anamount of heat as possible can be admitted into the working medium inthe thermosiphon. Furthermore, it is also advantageous if the recess isformed in the region of bearings of the electric motor. In addition tothe cooling of the rotor, the bearing temperatures are also evened outand reduced at the bearings, thus increasing the service life of thesehighly stressed wearing parts.

In one refinement, the shaft has a central section and an end sectionwhich is fixedly connected to the central section and to which theimpeller is fastened, the recess being of cylindrical design in thecentral section and the recess being of conical design in the endsection. This refinement ensures the circulation of the working mediumwhich has different states of aggregation during the operation of thepump. In contrast to known thermosiphons, the circulation of the workingmedium is not made possible by capillary forces but rather by rotationalforces. For this purpose, the conical design of the recess in the endsection of the shaft is necessary in order to press condensed workingmedium back in the direction of the rotor of the electric motor.

In one specific refinement, the electric motor and at least part of thecentral section of the shaft are arranged in a fluid tight manner in ahousing part, and the end section is arranged outside the housing part.In particular, the end section and the central section of the shaft aresurrounded on the outer circumferential side by a seal which may bearranged outside the housing part, fitting snugly onto a passage openingfor the shaft. The housing part may be, for example, a motor housingsurrounding the electric motor. In a practical refinement, the housingpart and the pump housing may be combined with each other. The sealensures that the fluid conveyed by the impeller cannot come into contactwith components of the electric motor, which could result in thedestruction thereof.

According to a further refinement, a device with spokes extendingradially from a central hub is provided in the conical recess of the endsection in order to improve the formation of a film of condensate of theworking medium on the conical wall of the end section. The device may bearranged in the conical recess and is intended to improve thecirculation of the working medium in the thermosiphon.

It is furthermore expedient if the ratio of the diameter of the recess,in particular in the central section, to the diameter of the shaft issuch that at least a predetermined torque can be transmitted to theimpeller. By the provision of a recess in the shaft, the torque whichcan be transmitted by the electric motor to the impeller is reduced. Inthis structural refinement of the thermosiphon, care should therefore betaken to ensure that a torque which is not less than necessary can stillbe transmitted by the shaft to the impeller. The provision of thethermosiphon in the shaft may possibly result in the diameter of theshaft having to be increased in order still to be able to meet thenecessary operating parameters of the pump.

It has furthermore been shown that the thermosiphon is particularlyefficient if the wall of the recess is rough. This means that, inparticular when making the recesses in the central and end sections ofthe shaft, the walls do not have to be finished in a particular way. Onthe contrary, it has been shown that the thermosiphon is most efficientif, after the recess has been made, no further recess machining stepstake place. Thus, in addition to a maximum increase in the efficiency,the costs for producing the thermosiphon can be kept low.

It is furthermore expedient if the working medium is placed into therecess under vacuum and, by sealing the recess permanently without anyloss. A refrigerant, in particular water, FC72, R124a, R600a, isobutane,etc., having an evaporation temperature of less than 100° C. is providedas the working medium. In principle, any refrigerant which has anevaporation temperature which is lower than the heat generated by therotor of the electric motor is suitable as the working medium.

In a further refinement, an end of the shaft which is outside thehousing part and is opposite the end section has a hub which is providedfor connection to a fan wheel for cooling the electric motor. Theadditional fan wheel can constitute a further heat sink for thethermosiphon. In principle, however, the refinement of the thermosiphonwith the impeller as a heat sink renders the provision of a further fanwheel unnecessary.

According to a further refinement, in an installation situation, theshaft is mounted horizontally or is mounted in such a manner that, withrespect to the direction of gravitational force, the impeller on the endsection of the shaft is located higher than the central section of theshaft. Both of these cases ensure that the thermosiphon is capable offunctioning in order to reduce the temperature of the rotor of theelectric motor. In other differing installation situations, cooling ofthe rotor can no longer be ensured. Although, then, the efficiency ofthe pump can no longer be increased, operation of the pump with theconventional efficiency is readily possible.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages will become more apparent andmore readily appreciated from the following description of an exemplaryembodiment, taken in conjunction with the accompanying drawings ofwhich:

The single figure shows a section through a pump used, for example, as acirculating pump in a heating circuit

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings, whereinlike reference numerals refer to like elements throughout.

The pump which is illustrated in the figure has an impeller 2 which isarranged in a two-part pump housing 1 a, 3. The pump housing 1 a has apump inlet 1 c, for example, from a heater, which opens into acollecting duct 1 b. The collecting duct 1 b extends spirally in theradial direction of the impeller 2 and opens into a pump outlet 1 d ofthe pump housing 1 a. The pump outlet 1 d is connected, for example, toan inlet to a radiator. In the exemplary embodiment, the pump housing 3is formed integrally with a motor housing 5 and has a passage opening 14for a shaft 7 which connects the impeller 2 mechanically directly, i.e.without an intermediate gear mechanism, to a rotor of an electric motor6. The electric motor 6 is arranged in the motor housing 5. In order toobtain sealing of the electric components provided in the motor housing5 from the fluid, for example water, conveyed by the impeller 2, a seal4 is provided outside the motor housing 5 in the region of the passageopening 14. The seal 4 fits snugly onto the outer edge of the passageopening 14 and is connected to a disk spring 13 which is arranged on theouter circumferential side of the shaft 7.

The shaft 7 is designed in two parts and has a central section 9 a, 9 b(having different diameters merely by way of example) and an end section10 connected to the central section. A recess which is provided withrespect to the axis of rotation is formed in the central section 9 a, 9b and in the end section 10. In the central section 9 a, 9 b, the recessis of continuous cylindrical design. In the end section 10, the recessis of conical design. As can be gathered from the figure, the impeller 2is connected to the end section 10 of the shaft 7. The central section 9a, 9 b and the end section 10 are connected to each other in such amanner that a working medium which is placed into the recess 8 undervacuum is arranged in the recess permanently without any loss. Arefrigerant having an evaporation temperature of. e.g., less than 100°C. is provided as the working medium in the recess 8. The refrigerantused may be, for example, water, R124a, R600a, FC72, isobutane, etc.

The provision of the recess 8 in the shaft 7 with the described shape ofthe recess in the central section 9 and in the end section 10 and withthe refrigerant being placed into the recess 8 results in the formationof a thermosiphon which is arranged in the shaft and in which theimpeller 2, which is connected to the shaft, serves as a heat sink forthe refrigerant of the thermosiphon. The effect achieved by thethermosiphon is cooling of the rotor of the electric motor and of thebearings 15, 16 thereof. During operation of the electric motor,temperatures of approx. 150° C. to 300° C. are achieved in the vicinityof the rotor, as a result of which the refrigerant provided in therecess 8 begins to evaporate. In an installation situation in which theshaft of the circulating pump is mounted horizontally or is mounted insuch a manner that, with respect to the direction of gravitationalforce, the impeller 2 on the end section 10 of the shaft 7 is locatedhigher than the central section 9 a, 9 b of the shaft, the evaporatedrefrigerant is forced in the direction of the end section 10 of theshaft 7 because of the rotation of the shaft. The impeller 2 is arrangedin the fluid, which is at a maximum of 70° C., for example in the caseof a heating circuit, and constitutes a condenser of the thermosiphon.

Owing to the lower temperature of the impeller 2 and the conicalconfiguration of the recess 8 in the region of the end section, theevaporated working medium condenses and is pressed onto the wall of theconical recess of the end section 10 because of the rotating shaft 7.The conical design of the recess 8 in the region of the end section 10ensures that the condensed working medium is pressed in the direction ofthe central section 9 a, 9 b until the working medium enters, in turn,into the region of the electric motor 6 (and therefore of the heatsource) and is evaporated there again. The working medium thereforecirculates owing to this change in the state of aggregation betweenliquid and gaseous in the recess 8 of the shaft 7. Thus, waste heat istransported away from the electric motor and admitted via the impeller 2to the fluid which is conveyed by the latter. In contrast to knownthermosiphons, the circulation of the working medium of the thermosiphonformed in the shaft 7 is not based on capillary forces but rather on therotational forces which occur in the shaft 7 during operation.

As a result, the rotor of the electric motor 6 and the bearings 15, 16of the shaft 7 in the region of the electric motor 6 are thereby cooled,thus resulting in an increase in the efficiency. At the same time, theheat which is lost and is conducted away from the electric motor 6 canbe recycled into the fluid circuit in which the impeller 2 is located.

The exemplary embodiment, which is illustrated in the figure, of thepump has an optional hub 12 which projects with the shaft 7 out of themotor housing 5 and is arranged at that end of the shaft 7 which isopposite the end section. The hub 12 serves to accommodate aconventional fan wheel in order optionally to bring about furthercooling of the electric motor.

The ratio of the diameter of the recess 8, in particular in the centralsection 9 a, 9 b, to the diameter of the shaft 7 has to be dimensionedin such a manner that at least a predetermined torque can be transmittedto the impeller 2. In the exemplary embodiment illustrated, the shaft 7has sections of differing diameter and therefore differing wallthicknesses in its central section 9 a, 9 b in order to transmit therequired torque. This illustration is merely by way of example and isnot compulsory. Irrespective of the wall thicknesses of the shaft 7 indifferent sections of the central section 9 a, 9 b, the bore 8 in thecentral section 9 a, 9 b has the same diameter continuously, thusensuring circulation of the working medium in the recess 8.

When producing the recess 8 in the shaft, the wall of the recess 8 doesnot need to be finished. It has turned out on the contrary that thethermosiphon is much more efficient the rougher the wall of the recess 8is. However, it is expedient to remove lubricants which may have beenintroduced into the recess 8 in order to produce the latter, since thelubricants may have a disadvantageous effect on the state of aggregationof the working medium.

The thermosiphon provided in the shaft 7 of the circulating pump can beprovided in conventional pumps, for example circulating pumps, and inwhat are referred to as high efficiency pumps. If a thermosiphon isinstalled in a conventional pump, pumps having efficiency comparable tothe high efficiency pumps can be realized substantially more favorably,since materials which are more cost-effective can be used in theproduction of the pumps.

For example, in standard pumps having an asynchronous motor within therange of 10 to 20 kW, an increase in efficiency of 1.5% can be obtained.The provision of a thermosiphon in the shaft of a high efficiency pumpalso results in an improvement in the efficiency there, but the increasein efficiency is smaller than in conventional pumps since highefficiency pumps inherently already have lower losses.

A description has been provided with particular reference to preferredembodiments thereof and examples, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the claims which may include the phrase “at least one of A, B and C”as an alternative expression that means one or more of A, B and C may beused, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69USPQ2d 1865 (Fed. Cir. 2004).

1-14. (canceled)
 15. A pump, in particular a circulating pump,comprising: a pump housing having a pump inlet and a pump outlet; animpeller in said pump housing by which a fluid can be delivered from thepump inlet to the pump outlet; an electric motor having a rotormechanically coupled to said impeller via a shaft, whereby rotation ofthe rotor causes rotation of said impeller; and a thermosiphon in theshaft, cooling the rotor of the electric motor, said impeller serving asa heat sink for a working medium of said thermosiphon.
 16. The pump asclaimed in claim 15, wherein said thermosiphon in the shaft is formed bya recess, extending in a longitudinal direction, in which the workingmedium circulates owing to a change in state of aggregation betweenliquid and gaseous.
 17. The pump as claimed in claim 16, wherein therecess extends over an entire width of the rotor of said electric motor.18. The pump as claimed in claim 17, wherein said electric motor furtherincludes bearings, and wherein the recess is formed in a region of thebearings of said electric motor.
 19. The pump as claimed in claim 18,wherein the shaft has a central section and an end section, fixedlyconnected to the central section, to which said impeller is fastened,and wherein the recess includes a cylindrical recess in the centralsection of the shaft and a conical recess in the end section of theshaft.
 20. The pump as claimed in claim 19, further comprising a housingpart in which said electric motor and at least part of the centralsection of the shaft are arranged in a fluid tight manner, and whereinthe end section is formed outside said housing part.
 21. The pump asclaimed in claim 20, wherein said housing part includes a passageopening for the shaft, and wherein said pump further comprises a seal,surrounding the end section and the central section of the shaft on anouter circumferential side, arranged outside said housing part andfitting snugly onto the passage opening for the shaft.
 22. The pump asclaimed in claim 21, further comprising a device with spokes extendingradially from a central hub, provided in the conical recess of the endsection of the shaft to improve formation of a film of condensate of theworking medium on a conical wall of the end section.
 23. The pump asclaimed in claim 22, wherein each of the shaft and the cylindricalrecess has a diameter and a ratio of the diameter of the cylindricalrecess to the diameter of the shaft provides for at least apredetermined torque to be transmitted to said impeller.
 24. The pump asclaimed in claim 23, wherein the shaft has a rough wall bounding therecess.
 25. The pump as claimed in claim 24, wherein the working mediumis placed into the recess under vacuum and is maintained in the recesspermanently without any loss by said seal.
 26. The pump as claimed inclaim 25, wherein the working medium has an evaporation temperature ofless than 100° C. and is selected from a group consisting of water,R124a refrigerant, FC72 refrigerant, R600a refrigerant, and isobutane.27. The pump as claimed in claim 16, wherein the shaft has an endoutside the housing part, opposite the end section, with a hub providedfor connection to a fan wheel for cooling the electric motor.
 28. Thepump as claimed in claim 27, wherein, in an installation, the shaft ismounted horizontally or is mounted with respect to a direction ofgravitational force, said impeller on the end section of the shaft islocated higher than the central section of the shaft.